Filter types are addressed in Vacuum Cleaners
In some respects this is the safest option if you have doubts about the effectiveness of your filtration. In the sense that you do what filtering you can, but then dump the waste air outside. You may find it cheaper to heat the extra air that needs to come in to replace it rather than spend enough on the filtration to do the job well enough to eliminate the really dangerous fine particles.
--John Rumm 18:03, 11 December 2010 (UTC)